Decimal to Percentage

[Yuseph]

Hey guys,

Sth weird on my book. The author ask to convert a decimal into a percentage. To convert 0,015 to a percentage. Thats 1,5% of course. But the thing that totally overwhelm me is its that the decimal is out of context. How can you determine it s 1,5% if you dont know what the decimal of 100% is. To sum up whats this exercice about ??

 

[tkhunny]

It is a relatively common misconception to think of "%" as some kind of unit. It isn't. It's just another way to write a dimensionless number.

1% = 0,01 -- That's all there is to it. Nothing else to consider.

0,4 = 40% -- That's it. No other concern.

1 = 100% -- That "100%" is just another way to express the number 1.

This is why you would have to threaten me to get me to use a [%] button on a calculator. Unless it has some other function besides the conversion, it doesn't actually do anything.

The exercise just wants to see if you can move the decimal two places and then remember to put the "%" on there so you don't change the magnitude of the number.

0,015 - Start here.
1,5 - Yup! We can move the decimal two places.
1,5% - That was close! We almost changed the magnitude of the number. Now, we're back to where we started.

 

[Dr.Peterson]

The word "percent" literally means "per hundred", and I find it helpful to think of it as "/100". So 1.5% means 1.5/100 = 0.015. (Moves the decimal point 2 places to the left.)

Converting to percent, I use the fact that 100% is another way to write 1; so we just multiply by 1 in the form 100%: 0.015 = 0.015*100% = 1.5%. (Moves the decimal point 2 places to the right.)

This method reminds you when your answer has a "%" in it.

And the reason I never use the percent key on a calculator is that it does different things on different calculators. On some, it just multiplies by 1/100, while others use it differently when you multiply, add, or subtract, so that 30 + 5% gives 31.5, increasing the number by 5%.

 

[Yuseph]

Thanks guys.

Yea thats what i suspected. So using an example wiv a decimal over 1 wouldnt have made much sense.